Contact PD/PI: Patten, Carolynn Stroke is the leading cause of serious, chronic disability in adults worldwide. Over 750,000 new strokes occur in the United States each year accounting for over half of all acute neurological hospital admissions. While two- thirds of persons who suffer a stroke regain ambulatory function, the resulting gait pattern is slow, asymmetrical and metabolically inefficient. Walking dysfunction represents one of the greatest physical limitations post-stroke and improved walking is among the most frequently articulated goals of neurorehabilitation. To date, rehabilitation for walking dysfunction post-stroke has produced highly variable outcomes revealing minimal genuine change in walking function including walking speed or walking pattern. Our long term goal is to improve walking function in persons post-stroke. The objective of this application is to develop a prognostic indicator to determine the physiological potential to improve walking capacity following stroke. The rationale for our proposal stems from our previous work, which has identified distinct patterns of response to therapeutic intervention for hemiparetic walking dysfunction, `responders' and `non-responders'. Responders are characterized by significant changes in overground walking speed and multiple changes in spatio-temporal coordination. Non-responders produced minimal changes in overground walking speed and few, if any, changes in spatio-temporal coordination. While the presence of responders and non-responders in the post-stroke population is not surprising, at study baseline responders and non-responders could not be differentiated using clinical instruments of motor impairment, activity, or walking speed. Moreover, clinical characteristics of chronicity and severity failed to predict these patterns of response. Taken together our findings suggest the presence of intrinsic, as-yet-unidentified subject-specific characteristics that mediate successful recovery of walking function. Here we propose development of a prognostic indicator to identify: a) neurophysiologic deficits contributing to walking dysfunction and b) an individual's potential to improve walking capacity following stroke. Informed by our prior work, we recognize neurophysiologic function contributes to neuromechanical output during walking. Attainment of a threshold of neurophysiologic functioning will suggest the presence of a neurobiological substrate requisite to improvement in walking capacity. Thus we will be able to differentiate individuals with the capacity to respond to traditional interventions from those who may need more aggressive approaches to remediate neurophysiologic function. Keywords: stroke, locomotion, recovery, rehabilitation, biomechanics Project Summary/Abstract Page 6